Various techniques such as a technique using reference light and a stereo ranging technique using two or more cameras have been suggested as imaging techniques for obtaining two-dimensional array information about the distances to objects in the depth direction. Particularly, in recent years, there has been an increasing demand for relatively inexpensive products as novel input devices for consumer use.
In view of this, a compound-eye imaging device that has an imaging lens that can obtain a large number of parallax images and restrains decreases in resolution has been suggested. In this imaging device, an imaging lens is provided, and optical systems are provided as a re-imaging optical system between the imaging lens and an imaging element. As the optical systems, a microlens array having a large number of microlenses formed on a flat surface is used, for example. Pixels are provided below the microlens array at locations corresponding to the respective microlenses, and those pixels obtain images of the corresponding lenses. An image formed by the imaging lens is re-imaged on the imaging element by the re-imaging microlenses, and the re-imaged individual lens images are images with viewpoint shifts due to the parallax existing at the locations of the respective microlenses.
By performing image processing on the parallax images obtained from the large number of microlenses, the distance to the object can be estimated based on the principle of triangulation. Also, by performing image processing for combining those parallax images, a two-dimensional image can be reconstructed.
However, when the above described compound-eye imaging device is formed, there are decreases in light amount at locations where an imaged height of the imaging lens is high, and there are decreases in light amount around microlens images. In the pixels in the low-illuminance region having decreases in light amount, S/N ratios of signals are degraded.